Benzylidene biscresols



BENZYLIDENE BISCRESOLS David J. Beaver, Richmond Heights, Mo., and Richard 0. Zerbe, Nitro, W. Va., assignors to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Original application Oct. 26, 1951, Ser. No. 253,474. Divided and this application June 18, 1957, Ser. No. 666,465

Claims. (Cl. 260-395) R: i R i B; it R1 where is a radical derived from an aldehyde reactant, as for example formaldehyde, pyruvic aldehyde, butyraldehyde, a-ethyl-B-methyl acrolein, benzaldehyde, and the like, whereyR, is an alkyl group containing at least four carbon atomsand Where R is an alkyl 1 group, preferably a short chain alkyl group, can be readily formed by condensing the appropriate 2,5-dialkyl phenol andan aldehyde and comprise a new familyof highly useful antioxidants.

Dialkyl phenols suitable as starting materials for the v preparation of the new compounds may be prepared by a variety of methods, however the position of the alkyl I groups exerts a profound influence on the antioxidant properties and it is essential to employ phenols having the proper orientation of the alkyl groups. Exemplary of one suitable class of dialkyl phenols are the products prepared by alkylating a meta or 3-alkyl substituted phenol with a tertiary alcohol or olefin in the presence of sulfuric acid or phosphoric acid catalyst. This affords a convenient direct synthesis and the published evidence indicates that under these conditions the. alkyl group enters the 6-position. In any event this class of products have proven'to be satisfactory. Other methods of synthesis are equally well known and available for the introduction of normal alkyl groups. Examples of suitable dialkyl phenols together with their physical properties are listed below;

6-tert. butyl m-c resol, B.P. 130. c ./2 o mm.

'Z-tert. butyl S-ethyl phenol, B.P. 135138 C./20 mm.

1.6-.n-heptyl m-cresol, B.P. 126-l28 C./2.5 mm. 6-n-octy1 m-cresol, B.P. 141143 C./3 mm.,

6-n-decyl m-cresol, B.P. 146-147 C./2 mm. 6-n-dodecyl m-cresol, B.P. 183 C./3 mm. (M.P. 44 C.).

ice

Still further examples of suitable 2,5-dialkyl phenols CH3 CH2 R1 1? R17 where R is an alkyl hydrocarbon group and R is an alkyl group of at least four carbon atoms. Such compounds may be economically prepared and in general are characterized both by exceptional antioxidant properties and freedom from discoloration. They may therefore be employed in the manufacture of light colored rubber articles. Formaldehyde derivatives are efi'icient but less easily prepared. Derivatives of aromatic aldehydes are also antioxidants but less efiicient. Similarly compounds derived from substituted aldehydes, whether aliphatic or aromatic, have in general proved to be less efiicient antioxidants than those derived from the corre sponding unsubstituted aldehyde's. On the other hand the new compounds also comprise antiseptic and germicidal agents and for this purpose the most effective compounds have been obtained from substituted aldehydes. For example, 4,4-(p-hydroxy benzylidene)-bis.- (3-methyl-6-tert. butyl phenol) exhibits excellent antiseptic properties which properties are retained in the presence of soap. This subject matter is claimed in an application filed by one of us and others January 5, 1951, Serial No. 204,698, now US. Patent 2,678,302.

The condensation of the phenol and the aldehyde is usually carried out in a molar proportion of 2:1 in the presence of an acidic condensation catalyst, as for example, hydrochloric acid. Where desired solvents and/or dispersing mediums may be employed although the reactions are actually carried out in the absence of either. The following examples are illustrative of the preparation of the newcompounds. i

Example I To a suitable container was added 98.4 grams (substantially 0.6 mole) of 6-tert. butyl m-cresol, B.P. C./20 mm., 24.0 grams (substantially 0.33 mole) of butyraldehyde and 6 grams of concentrated hydrochloric acid, The

whereupon a mushy solid developed. The latter was steam distilled free of volatile matter. Thereupon the residue was taken up with benzene and washed free of acid withwater, whereupon the water-benzene mix was distilled ed and the mass evaporated to dryness. The white solid so obtained was recrystallized and gave a fine White crystalline product possessing a melting point of 210.2- 210.9 C. (corn) which was believed to be 4,4-butylidene bis-(6-tert. butyl m-cresol). Analysis for carbon and hydrogen gave 81.91% and 10.23%respectivelyas I compared to calculated values of 81.64% and 10.01%. i I. i Exqri1ple 2 V i i f i To a suitable container was added 82.1 grams (substantially 0.5 mole) of 6-tert. butyl m-cresol as described in the foregoing example, 18.0 grams (substantially, 0.25 mole) of isobutyraldehyde, and 4.7 grams of concen- Patented Jan. 31, 1961.

trated hydrochloric acid. The mixture was refluxed at 95 C. for approximately one-half hour. The reaction mixture was cooled and thereto was added 100 ml. of a liquid aliphatic hydrocarbon consisting chiefly of heptanes.

one of the antioxidants listed below. The respective stocks were cured in the usual manner by heating in a press at 126 C. for 45 and 60 minutes. The first column of data in the following table shows the percent The mix was agitated for 4 hours at 30-32" C. and the 5 retention of ultimate tensile strength obtained after aging White solid was filtered off, washed with several portions for 12 hours in an air bomb at 121 C. at 80 lbs./in. of the aforesaid aliphatic hydrocarbon and subsequently The figures are the averages for the two cures. The secdried. Upon recrystallization from benzene a white crysond column shows the resistance to discoloration. Samtalline product was obtained which possessed a melting ples of the cured stocks were exposed under an -S'-1 sunpoint of 228.9229.7 C. (com) and was believed to be lamp for 10 days. After exposure the light reflected from 4,4'-isobutylidene bis (6-tert. butyl m-cresol). Further the surface of the stocks was measured by means of a purification by recrystallization from heptane gave a Photovolt Reflectance Meter calibrated against reflectance product M.P. 229.8-230.7 C. Analysis for carbon and of standard MgO as 100%. 'The data shown are percent hydrogen gave'81.47% and 9.94% respectively as comreflectance of the 60 minute cures.

pared 'to calculated values of 81.64% and 10.01%. 15

The following crystalline compounds were prepared TABLE employing essentially the procedure of Example 2 by refluxrng a half gram mole or the appropr ate phenol and Antioxidant 'ig f g g g one-rourth gram mole of the aldehyde 1n the presence percent; 31106, of hydrochloric acid catalyst. The reaction times varied, P t these being determined by spot testing at intervals with a suitable solvent onprecipitant for crystal formation and 153311355i565Q-BEQBIQEBHt-Qaagabzz 35 -g 73 quenching the reaction when crystal formatlon was ob- 4,4-Benzylidene bis-(fi-tert. butyln-cresol)--- 68 60 served and before sufficient resin was formed to inter- 4Y4"ISbtY1i,dene 549ml-butylmflesm) 71 fere with the purification of the crystals. A heptane fraction as described in the detailed example was used Further examples of the new compounds were prepared except that No. 2 was precipitated by caustic soda from r m chlol'o-sllbstiiuted belllaldehydes- Approximately glacial acetic a id. 4 ml. of concentrated hydrochloric acid was added to No. 1. 4,4'-b enzylidene bis-(-tert. butyl m-cresol), a well-stirred solution of 0.5 gram moles of 6-tert. butyl M.P. 199.3199.8 C. (corn), pearly solid, from benzm-cresol and 0.25 gram moles of the aldehyde. The aldehyde and 6-tert. butyl m-cresol, reaction time V2 reaction mixture was held at about 95 C. and tested hour. Carbon found 83.54%, calc. 83.62%. Hydrogen periodically for crystal formation by adding one ml. of found 8.55%, calc. 8.71%. the reaction mixture to 3 ml. of heptane and when crys- No. 2. 4,4'-(p-hydroxy benzylidene)-bis-(6-tert. butyl tal formation was noted the reaction mixture was m-cresol), M.P. 262.4263.1 C. (corn), lemon yellow quenched by adding 100 ml. of heptane and the mixsolid, from p-hydroxy benzaldehyde and 6-tert. butyl ture cooled. The crystalline product was filtered, washed rn-cresol, reaction time /2 hour. Carbon found 80.33%, with cold heptane and recrystallized. from the same solcalc. 80.53%; Hydrogen found 8.10%, calc. 8.39%. vent. They possessantiseptic and germicidal properties.

TABLE II Aldehyde Time, M.P.,"O Empirical Cale, Found,

- Hrs. Formula percent percent v Carbon--- 71.73' 71. 1

2,4-Diehlorobenzaldehyde 4 2093-2104.. 029113401202"--- {Hy-hogan.-. 7.06 6. 6

. Chlorine.--. 14. 61 14.

a Carbon. 74.58 74. 6

fi-Ohlorosalicylaldehyde 6 214.2215.9.- 0251 13 010: {Hydrog 7. 7. 9

. Chlorine 7.59 7. 8

' p Carbon... 77.22 '77. 0

0Ch1orobenzaldehyde as 226. 3-226. 9-. 02.11. 010, {livdrogemn 7. 82 7.16

, Chlorine... 7.86 8.

No. 3. 4,4'-(o-hydroxy benzylide'ne)-bis-(6-tert. butyl This application is a division of co-pending applicam-cresol), White solid from toluene M.P. 216.7217 C., tion Serial No. 253,474, filed October 26, 1951, which reaction time /2 hour. Carbon ,found 80.37%, calc. latter is a continuation-in-part'of application Serial-No.

80.53%. Hydrogen found 8.59%, calc. 8.39%.. This 55 159,128, filed April 29, 1950, now abandoned. product was prepared from salicylaldehyde and 6-tert. What-is claimed is: butyl m-cresol. 1. As a composition of matter a compound-of the No. 4. 4,4 (3,4 dimethoxybenzylidene)-bis-(6 -tert. structure a butyl m-cresol), white solid from heptane M.P. 231.2- R,' R2 I 231.9C., from veratraldehyde and 6-tert. butyl m-cresol, 0 30. reaction time /2 hour. Carbon found 78.17%, calc. .1 I 78.12%. Hydrogen found 8.60%, calc. 8.46%. i j 4 1 B As illustrative of the antioxidant properties of the where R is an aromatic radical. of the'benzene series, new dihydroxy diaryl methanes several rubber base R is an alkyl group containing at least 4 but not more stocks were compounded comprising than 12 carbon atoms and R is'an. alkyl group con- V r I taining less than 3 carbon .atoms. Pale crepe rubber ?i f f% g 2. As a composition of matter a compound of the Zinc oxide V 60.0 structure 6 r r r Lithopone 20.0 CH3 H a Sulfur 2.0 O- 0H 7 Diphenyl guanidine phthalate 0.825 1 52 25 3 azyl thlobenzoate where R is an' aromatic radical of the benzene series and R is a branched chain. alkyl group containing at To each base stock was added 1.0 part by weight of least4 but less than 9 .carbo'n atoms. f i 7' v 5 6 3. As a composition of matter a compound of the 5. As a composition of matter a compound of the structure structure on: CH3 cm CH:

C R 1 5 a): (CH2): (CH1): (CH5):

where R is an aromatic radical of the benzene series.

4. As a composition of matter a compound of the 0 H structure 10 References Cited in the file of this patent CH: H CH; HO O UNITED STATES PATENTS O my C 1 15 2,515,907 Stevens et a1. July 18, 1950 (0119a (C 9: 2,559,932 Briggs et a1. July 10, 1951 2,570,402 Stevens et a1. Oct. 9, 1951 2,734,088 Knowles et a1. Feb. 7, 1956 

1. AS A COMPOSITION OF MATTER A COMPOUND OF THE STRUCTURE 